Researchers at Microsoft Research India have developed a new alternative acoustic-based data transfer system with capabilities similar to Near Field Communication (NFC) that requires no specialized wireless hardware.
Derived from radio-frequency identification (RFID) technology, NFC enables low data rate, bidirectional communication between devices in close proximity in a peer-to-peer manner. Most often used for contactless payments or data exchange between two devices, the technology provides a number of perceived benefits when compared with Bluetooth and Wi-Fi, including faster connection time and lower power consumption. In addition, because the devices are required to be in such close proximity when using FNC technology, the likelihood of interference is much lower. However, while NFC technology is in use as an instant payment method by companies such as Google and MasterCard, it’s still far from achieving widespread adoption due in part to the lack of NFC-dedicated hardware in some leading smartphone models.
The new software-based ‘Dhwani’ is the result of a Microsoft Research India (MRI) project to enable NFC-like capabilities in existing smartphones that do not have the hardware needed for NFC. Dhwani relies on a smartphone’s microphone and speakers to securely exchange data, achieving speeds of up to 2.4Kbps. While falling short of the peak rate of 424Kbps possible with NFC, researchers Rajalakshmi Nandakumar, Krishna Kant Chintalapudi, Venkata N. Padmanabhan, Ramarathnam Venkatesan say Dhwani’s speed is sufficient for most existing NFC applications.
“In order to enable Dhwani, we implemented an Acoustic Software Defined Radio (ASDR) on the mobile devices that uses speakers and microphones to receive and transmit data,” the team said in a report published on the Microsoft company website.
“Our ASDR design had to address several challenges unique to the nature of acoustic signal propagation and speaker-microphone characteristics. For example, we found the gain of the speaker-microphone combination in phones to be extremely non-uniform across the range of frequencies (frequency selectivity), presumably due to the mechanical properties of their electro-mechanical parts (e.g. vibrating membranes). Furthermore, the high degree of ringing in the acoustic channel (reverberations), compared to radio frequency, rendered the existing RF self-interference cancellation techniques inadequate.”
To remedy these issues, the team developed JamSecure, a novel self-jamming technique that uses the receiver to intentionally jam the signal it is trying to receive and then employs self-interference cancellation to successfully decode the incoming message.
The researchers believe that in addition to removing the need for specialized hardware, Dhwani also provides more transmission security than NFC.
“Conventional NFC does not incorporate any security at the physical or MAC layers, since the short range of communication (about 10 cm) is in of itself presumed to offer a degree of protection,” the research team said. As part of their research, the team demonstrated that it is possible to monitor NFC communications from 20-30cm away using an oscilloscope and a standard tag antenna, and believe that such snooping would be possible from up to a meter away with a more sophisticated antenna.
